In the prior art, there are a wide variety of different treatment procedures with the aim of correcting refractive errors in the human eye which are already known. The aim of these operative methods is to alter the cornea in a targeted manner in order to influence the refraction of light in the eye. Several operative methods are used for this purpose. The most common method is the so-called laser in-situ keratomileusis, also known as LASIK. In this method, a cornea flap is detached from the cornea surface and folded to the side. This flap can be removed using a mechanical microkeratome or using a so-called femtosecond laser keratome, as sold by e.g., Intralase Corp., Irvine, USA. In a LASIK operation, after the flap has been detached and folded to the side, an excimer laser is used to remove the cornea tissue under the flap that has been exposed in this way by application of ablation. After the body under the cornea surface has been vaporized, the cornea flap is then folded back into its original place.
The use of a laser keratome to expose the flap is advantageous compared to a mechanical knife because it improves the geometric precision and reduces the frequency of clinical complications. In particular, the flap can be created with a much more consistent thickness when a laser is used. The cut edge is also formed more precisely, which lowers the risk of healing problems with this border area, which still remains after the operation. However, a disadvantage with this procedure is that two different treatment devices must be used: firstly, the laser keratome to expose the flap, and secondly, the laser to vaporize the cornea tissue.
These disadvantages are resolved by a procedure that was most recently implemented by Carl Zeiss Meditec AG and is known as FLEX (Femtosecond Lenticule EXtraction). In this lenticule extraction procedure, a short-pulse laser, for example a femtosecond laser, is used to create a geometrical cut in the eye's cornea which separates the cornea body (so-called lenticule) within the cornea. This is then removed manually by the operator after the flap covering the lenticule has been folded to the side. One advantage of this procedure is that the quality of the cut is improved even further by the use of a femtosecond laser combined with a curved contact lens.
It also means that only one treatment device is required; the excimer laser is no longer used. This method also avoids the risks and limitations associated with the excimer laser.
A development of the FLEx procedure will be referred to in this literature as the SMILE procedure, for which no flap is created, but rather only one small opening cut is made to access the lenticule under the so-called cap. The separated lenticule is extracted through this small opening incision, meaning that the biomechanical integrity of the anterior cornea is not impaired as much as with the LASIK procedure or other similar methods. This also means that on the surface, fewer nerve fibers are cut in the cornea, which will very likely have a positive effect on the recovery of the cornea surface's original sensitivity. The dry eye symptoms which often have to be treated after the LASIK procedure are therefore reduced in terms of severity and duration. Other complications after LASIK, usually associated with the flap (e.g., flap shift, wrinkles, ingrowing epithelium in the flap bed), occur more rarely without the flap.